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Thinning of kaolin slurry
Vlasák, Pavel ; Chára, Zdeněk ; Konfršt, Jiří
After mixing kaolin with water attractive and repulsive forces between kaolin particles initiate process of coagulation and peptisation, respectively. The coagulation process in the kaolin slurry gives rise to voluminous aggregates of kaolin particles, where a great deal of water is fixed.
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Hydraulics of overflowed bridge
Chára, Zdeněk ; Vlasák, Pavel
The paper deals with an open channel flow around model of a bridge when the water depth is higher than height of the bridge opening. Both the pressured flow through bridge opening and free surgace flow over the model were studied. For both cases discharge coefficients were determined and for overflowed model also the velocity profiles were measured to evaluate the ratio of discharges going below and over the bridge model.
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Laminar and turbulent transition in fine-grained non-Newtonian slurries
Vlasák, Pavel ; Chára, Zdeněk
The transition from laminar to turbulent flow regime is very important for design and operation of non-Newtonian slurries pipelining. The paper deals with experimental investigation of laminar/turbulent transition, flow behaviour and rheological parameters of fine grained highly concentrated non-Newtonian slurries in horizontal pipes. Research is focussed on different character of slurry behaviour in laminar and turbulent region and verification of prediction turbulent model.
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Drag reduction of dense fine-grained suspensions
Vlasák, Pavel ; Chára, Zdeněk ; Štern, Petr
The effect of addition of the sodium carbonate and soda water-glass and their concentration for different kaolin slurry was investigated. The significant decreasing of the apparent viscosity and the yield stress was observed due to the addition of the both peptising agents. The viscosity difference between coagulated and peptised slurries can achieve values of several orders of magnitudes depending on peptising agent concentrations. The modification of physico-chemical environment of the transported slurry can be used also for another fine-grained dense hydro-mixture, e.g. for different mine tailings or for bauxite residue.
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Laminar and turbulent flow of dense kaolin and ash hydromixtures
Vlasák, Pavel ; Chára, Zdeněk
Two turbulent models based on rheological parameters (Wilson, Slatter) for concentrated kaolin and ash slurries were analysed. The flow behaviour of slurries was investigated on tube viscometer. It was find out that the flow behaviour index n decreases, while yield stress and fluid consistency K increase with increasing concentration. The both turbulent models can be used for prediction of flow behaviour of kaolin and ash slurries in the turbulent regime if the flow behaviour index n is determined from turbulent data.
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